Vehicles using electric power for all or a portion of their motive power may provide a number of advantages as compared to more traditional gas-powered vehicles using internal combustion engines. For example, vehicles using electric power may produce fewer undesirable emission products and may exhibit greater fuel efficiency as compared to vehicles using internal combustion engines (and, in some cases, such vehicles may eliminate the use of gasoline entirely, such as in certain types of plug-in hybrid electric vehicles). As technology continues to evolve, there is a need to provide improved power sources, such as battery systems or modules, for such vehicles. For example, it is desirable to increase the distance that such vehicles may travel without the need to recharge the batteries. It is also desirable to improve the performance of such batteries and to reduce the cost associated with the battery systems.
The use of newer battery chemistries and the desire to enhance performance of electric vehicles have given rise to new design and engineering challenges. For example, it may be desirable for such battery systems to exhibit improved thermal characteristics under short circuit conditions. One test that probes the thermal characteristics of a battery system under a short circuit condition is the blunt nail penetration test. During this test, the battery system is typically punctured with a nail, and the maximum temperature reached by the system is measured. While some current battery systems have been developed that seek to reduce the maximum temperature that is measured during such tests, many current battery systems, when probed in this manner, exhibit sparking or flaming behavior due in part to the occurrence of local hot spots that arise from the short circuit condition. Accordingly, it would be desirable to provide an improved battery system for use, for example, in vehicles using electric power, that is capable of exhibiting improved thermal characteristics during short circuit conditions.